Put the tomatoes, cut-side up, on a large baking sheet lined with baking parchment. Shake 1 tsp sea salt and drizzle with 1 tbsp. oil. Next, sprinkle over the thyme. Roast for 30 to 40 minutes, or until the tomatoes are slightly shriveled but still juicy.
Mix together the ricotta and parmesan. Season if needed.
Brush the bread with the rest of the oil and cook for 2-3 mins on each side.
Top with the ricotta mixture, tomatoes, prosciutto and a drizzle of olive oil. Add the optional rosemary to garnish.
